Hygroscopic element for indicators and the like



March 5, 1935. w Q Goss 1,993,441

HYGROSCOPIC ELEMENT FOR INDICATORS AND THE LIKE Filed June 13, 1951 w i l f5, j] 5, BY Waan/6.6055

j ATTQRNEYS Patented Mar. 5, v1935 PATENT OFFICE LQSALI HYGBOSCOPIC vELEMENT FOB' INDICATOR `AND THE LIKE A Worth C. Goss, Seattle, Wash., assignor to Humidity Control Company Application June 13, 1931, Serial No. 544,244

lilClaims.

This invention relates to improvements in indicating and controlling elements especially usei'ul in connection with indicating and controlling instruments which operate under influence of 5 and in accordance with changes of relative humidity of the surrounding air; it being the principal object of this invention to provide a hygroscopic indicating element for instruments oi the above character having an improved form of .construction which eliminates the possibility oi' the parts constituting the element being subjected to undue strain by reason of unequal expansion or contraction which would cause inaccuracy and nally necessitate a recalibration. Another object is to provide a methodV of treating the hygroscopic material oi the element to greatly increase its sensitivity.

Explanatory to the present invention, it will be explained that heretofore-instruments oi this character, in general, have employed an indicating or controlling element made up of two strips of flexible materials glued or otherwise xed together, preferably in accordance with disclosures of my co-pending application Serial No. 493,804, led November 8, 1930, for an improvement in hvgrostatic.- control; one of these strips being a material which willv contract and expand in length in accordance with changes of humidity to a greater extent than the otherv strip, thus to cause the element to bend one way or the other to indicate the degree of any change or to actuate a con= trol switch, or the like. It has been customary to employ two strips of woodl or other equivalent materials for this purpose, and to glue the strips firmly together; the wooden strips in this instance v having diil'erent characteristics 'or properties causing them to be diierently aiected by atmospheric conditions and to thus cause the instrument to function. Elements oi this type of constructionoperate with a satisfactory degree of accuracy only within certain limits, and then will give satisfactory results only so long as the hygroscopic materials are not subjected to strain beyond their elastic limits. However, to keep within safe limits would be to so restrict the utility of the instrument that it would be undesirable for practically all commercial purposes, since any indicator or controller so constructed, to bevcommercially desirable, must be able to indicate correctly the usual'variation o1 relative humidity from one to ninety per cent.

strains or stresses are set up in the strips along the connected surfaces by reason of one of the strips expanding or contracting to a greater extent than the other, and this strain places a limitation on the range of the instrument. It is readily apparent that when the strips are glued tightly together, their attached surfaces cannot move relative to each other, and thus one strip along its glued surface is placed under tension and the other strip along the glued suri'ace is placed under compression. These opposing strains on the strips are in accordance with the degree of change of humidity and should either piece be stressed beyond its limit of elasticity permanent case hardening" or set in the element will be the result and the piece will not again assume its original position for any certain degree of relative humidity. This would necessitate a readjustment and change of calibration in `order togive correct readings.

""' for cztrolling, and which will operate accurately under all conditions of relative humidity and will accurately accommodate the full range for an indefinite period of time without any material change in its original calibration.

More specifically stated, the present invention resides in the provision of an indicator or con. trolier element in which the two complemental strips of material or materials which cause functioning of the element are connected by an interposed, elastic member which permits of movement of one strip relative to the other in accordance with humidity changes, yet holds them iirmly and securely in proper functional relationship, without causing any detrimental strain to be placed on either strip regardless oi their degree of iiexure; that is, a connecting strip that insures against straining the lstrips beyond their elestic limit.

It is also an object o i the invention to produce a hygroscopic element'that is well adapted for4 use in various kinds ot instruments, both for indicating or for'controlling, which operate in Yaccordance with and under control of atmospheric changes.

It is also an object of this invention to provide an instrument for indicating atmospheric conditions and which is of novel construction, and embodies as the principal parts thereof an indicating element made in accordance with the present invention, and a thermometer.

In accomplishing these and other objects of the invention, I have provided the improved details of construction, the preferred forms of which are illustrated in the accompanying drawing, wherein- Fig. 1 is a front view of an instrument embodying improved details of construction according to the prent invention.

Fig. 2 is a vertical cross section taken on line 2\2 in Fig. 1.

Fig.3 is a front view of the hygroscopic ele ment as mounted on a support within the insn'ument.

Fig. 4 is an enlarged longitudinal section of a portion of the hygroscopic element.

Fig. 5 is a cross section of the same.

Fig. 6 is a perspective view illustrating an alternative form of element, a part being broken out for better illustration.

Fig. 7 is a view illustrating a form of construction for increasing the force of the instrument when used as a controller.

Fig. 8 is a view illustrating` aconstruction for multiplying the movement of the element.

The drawing is intendedv to illustrate some of ent element and it is not intended that they shall convey theidea that these are the only applicationsl to which it may bev put, since it is to be understood that the element iswell adapted to all those uses to which other elements of a hygroscopic character have heretofore been applied, or to which they. may be applied. Referring more in detail to the drawing- I 1 designates the housing or mounting for the instrument, and it comprises an enclosed compartment 2 over which a back or cover plate 3 is removably fitted. This housing or mounting piece may, if such is desired, be of an ornamental character as shown, orv may be of any other suitable form, and it is provided across the top with a forwardly opening window 4 of arcuate form, back of which a dial plate 5 is supported, there being an open space as at 6 between the plate and the front wall of the housing for the movement therein of an -indicator hand or pointer, as will presently be described, which co-operates with marked graduations, as at 'I on the plate, whereby the relative humidity will be indicated. 'Ihe indicating mechanism comprises the hand or pointer 8 which is pivotally mounted at its lower end by a supporting stud 9 that isv iixed in a bearing or support 10 carried on thev inner face of the cover plate 3 near its lower edge. The

pointer is directed upwardly within the housing and has an outwardly oiset end portion extending through the open space 6 for travel along the forward side of thev graduated dial plate. In the lower end portion of the pointer is a longitudinally extending slot'12 Within which a pin 13, that is fixed in the lowerend of a hygroscopically actuated element 15, is operable to cause movement 'of the pointer in accordance with the movement of the element to thus indicate. by reference to the graduations on the dial plate, the changes in relative humidity of the atmosphere.

A novel feature of this invention resides in the construction of the hygroscoplc element desig-l nated in its entirety by reference character 15. The element consists of two exible strips 16 and 17 of material, and these are glued, cemented or otherwise attached to the surfaces of an interposed strip 18 of a flexible, elastic material such as rubber, cork, or the like. I n some instances it may be desirable'to connect the parts by rivets extended through the rubber or by the other means of attachment which would permit oi the desired flexing and relative movement of parts without any functional interference.

The interposed strip 18 preferably would be continuous, but it is to be understood that satisfactory results might also be obtained by use of short sections 18 at spaced intervals along the element as shown in Fig. 6. These should not be spaced so far as to nullify the action of the element by reason of relative longitudinal movement. One of these outer strips must be hygroscopic, and one only partially or preferably nonhygroscopic.` l

It has been found most practical to employstrips of wood for the outer side portions of the element and to glue them securely to the opposite surfaces of a strip of rubber. Very satisfactory results have been obtained by use of a strip of eastern hard maple on one side of the element of end grain cut to expose the open pores to the atmosphere to render it more sensitive. The other side strip is very satisfactory when made of western red cedar of longitudinal cut so as to be aected tothe least possible extent by atmospheric changes. Also this latter strip may be painted to increase its resistance to atmospheric changes. Tests have shown that the maple strip will change 10% in length with a changein moisture content from 1% to 25% while the cedar will change .01% in length for a like change in moisture conditions.

As a matter of explanation, it will here be stated that by end grain cu is meant a strip wherein the direction of grain is directly through the strip from face to face. This would mean that the pores of the strip will open to the flat inner and outer faces of the strip. vBy longitudinal cu is meant that the fiber forming the grain extends lengthwise of the strip, thus the -pores would extend lengthwise and would not open to atmosphere except at the ends of the strip.

These two strips, after being attached or applied to the interposed rubberv strip, are fixed rigidly at one end to a block 20 fastened centrally to the upper edge of the cover plate 3 with the stud or pin 13 at the lower end of the element extended into the. slot in the lower endv portion of the pointer.

` Assuming the element to be so constructed and vapplied in use as in Fig. 1, it is quite apparent tent to which the element is flexed in one direction or the other, there will be no detrimental strain or stress on either of the strips, for the reason that flexibility of the interposed strip of the other and still retains them functionally connected.

It is to be understood that I do not wish to con.- ne the element to the use of wooden strips or to the use of a rubber connecting and cushioning strip, for it is quite possible to satisfactorily employ other hygroscopic materials in a like inanner. For instance, a strip of wood in connection with a flexible metallic strip may serve the purpose, so long as there is an interposed element which will operate to the same purpose as rubber. such as cork or any other elastic materiai; the best results being obtained however when the interposed, elastic element is non-hygroscopic.

In the present drawing,` in Figs. 1 and 2, I have disclosed an instrument for indicating atmospheric conditions, that is, the relative humidity of the atmosphere and also the temperature. In such instruments it is not sumcient to provide only for indicating the relative humidity of the atmosphere, for the reason that a certain relativey humidity which may be healthful at one ternperature will not be healthful at another ternperature.

mosphere with respect to humidity, but also with respect to its temperature. Therefore, for convenience, a thermometer 24 is mounted in a vertical opening 25 in the front wall of the housing upon a panel 26. Thus when a reading of the upper dial is made, notation of the temperature may be made at the same time, and from these readings it may be determined whether or not proper atmospheric conditions exist.

Devices of the present character are very desirable for home use so that proper conditions of temperature and humidity may be maintained. However. the instrument is not to be connned to this particular use.

In Fig. 'I I have illustrated a form of arrangement -for increasing the strength ofA the instrument, more especially when it is to be used as a controller. In this arrangement I provide a xed mounting piece 40 of a non-hygroscopic character in which a plurality of elements 15 like those previously described .in detail, are xed, and which extend substantially at al right angle to the mounting piece. At their lower ends these elements are pivotally connected to a link 4l for parallel movement, and the link has a pin 42 at its end for the actuation of a switch, or the like.

- In this form of arrangement, the power to be derived from the instrument may be increased in accordance with the number and character of elements employed.

In Fig. 8 is illustrated an arrangement of elements for multiplying movement ofthe instrument. In this construction there is a plurality of elements l arranged in end to end connection in a series of upright and inverted Vs. The first element, a, of the series is ilxed at its upper end in a block 45. The second element, 15b, is mounted in a block 46 xed to the lower end of the first element to extend in an upward angular relation to the first. The third element, 15e, of the series is fixed in a block 47 attached rigidly to the upper end ofthe second element. This arrangement of elements is continued to the exddheelement is more or less in accordance with the width of the hygroscopic element and the movement dependent also on its length.

To determine proper air conditions one shouldmow not only the condition of the' at- As was previously stated, one of the objects of t the invention is to treat the hygroscopic material in a novel manner to add to its sensitivity. In a preferred treatment of the wooden strip which controls movement of the element the cell substance is removed to leave the pores open to air, thereby greatly increasing its aected surface. This treatment consists of boiling the wood in water or other suitable material 1. plurality of times or sumcient that the cell substance is dissolved or washed out from the pores, after which it is properly dried to prevent warping. Wood so treated has been found to be exceedingly more sensitive than untreated wood and therefore is more desirable for instruments of this character. The usual treatment is three separate boilings in fresh water and then an even drying by forcing air evenly across the piece..

It is desired to point out that in each and every one of the instruments above described, the emciency and continued accuracy of the instrument is primarily dueto the details of construction of the element or elements 15 employed therein. These elements are featured by the elastic strip or sections interposed between and joining the two complemental outer strips, one of which is of a hygroscopic character and the other preferably non-hygroscopic. It is thought well to point out that the rubber strip used, or its 'equivalent, should have suillcient stretch lengthwise to permit expansion and contraction of the hygroscopic element to its limits without placing the piece under detrimental strain. and the thickness of the rubber strip also should be so limited that it would 'not stretch in the direction of its thickness to an extent that he movement of the hygroscopic strip relative to the non-hygroscopic strip would be nullified.

Having' thus described my invention, what I claim as new therein and desire to secure by Letters Patent isl. In an vinstrument of the class described, a

hygroscopic element comprising co-extensive flexible strips Joined functionally by interposed elastic means; one of said strips being more sensitive to moisture than the other.

2. In an instrument of the class described, a hygroscopic element comprising co-extensive nexible strips joined throughout their eeotive lengths by interposed elastic member permitting relative movement o the co-extensive strips in a longitudinal direction; one of said strips being more sensitive to moisture than the other.

3. In an instrument of the class described an element comprising co-extensive, exible strips of diiiferent4 character hygroscopically, and elastic means interposed between said flexible strips at spaced points and functionally joining them.

e. In an instrument ci the class described, an element adapted to be operated incident to humidity changes and comprising two co-extensive, flexible strips of different hygroscopic character joined together throughout their effective lengths by interposed elastic means permitting lateral exing of the element and relative longitudinal adiustment of the strips without detrimental strains or stress by reason of the connection.

5. In an instrument of the class described, an

element adapted to be actuated incident to humidity changes and comprising two co-extensive,

l exible strips, one of which is of hygroscopic nature; said strips being joined throughout their effective lengths by an interposed strip of elastic material oi non-hygroscopic character.

6. An element of the class described comprisving two co-eirtensive, flexible strips of different hygroscopic character, and an interposed strip of elastic material with opposite faces cemented to the adjacent faces of said co-extensive strips to functionally join them throughout their effective lengths; said interposed strip being adapted t0 stretch in' its longitudinal direction to accommodate the relative movement of the strips in that direction, but having a negligible amount of stretch in the direction of its thickness.

7. A hygroscopic element comprising co-extensive, flexible strips of materials of diiferent character` hygroscopically, and an interposed strip of an elastic material functionally joining said co-extensive strips throughout their effective lengths; said interposed strip being adapted to stretch in a lengthwise direction sumciently to permit relative longitudinal movement of the strips for the full range of movement but maintaining necessary tension between the strips to cause functioning of the instrument by reason of the relative longitudinal movement.

8. An instrument of the character described including a hygroscopic element fixedly supported at one end and'` movable in accordance with humidity changes; said element comprising two co-extensive strips of material of different hygroscopic nature and joined functionally throughout their eective lengths by an interposed strip of an elastic character permitting flexing of the element and relative adjustment Y of the co-extensive strips without causing detrimental stress or strain by reason of their connection.

9. -A hygroscopic element comprising two, coextensive flexible strips joined throughout their effective lengths by an interposed strip of flexible, cushioning material of a non-hygroscopic character permitting relative longitudinal movement of the strips Joined thereby without causing harmful stress or strain by reason of the connection; one of said strips being of wood of tangential end grain or radial end grain cut and the other being of wood of longitudinal cut.

10. A hygroscopic element comprising two coextensive wooden strips of a flexible character, and a strip of rubber interposed between the wooden strips and glued or otherwise attached thereto throughout their eil'ective lengths; one K WORTH C. GOSS. 

